Traders work on the floor of the New York Stock Exchange. / Ramin Talai,e Getty Images

by Adam Shell , USA TODAY

by Adam Shell , USA TODAY

NEW YORK -- Ask pretty much any money manager or economist on Wall Street the question: Are lawmakers crazy enough to let the U.S. default on its debts? And the answer invariably is: "No way!"

What if they're wrong?

When discussing the odds of the U.S. not paying its bills for the first time in its history, an event the U.S. Treasury says could occur as early as Oct. 17 and usher in a financial crisis on par, if not worse, than the 2008 financial storm, Wall Street keeps saying the odds are long. As in really, really, really long.

Adam Parker, chief U.S. equity strategist at Morgan Stanley, puts the chance of a default at "zero percent." Joseph LaVorgna, chief U.S. economist at Deutsche Bank, says it is "effectively zero." Craig Johnson, senior technical research analyst at Piper Jaffray, also says it won't happen, saying that if it does voters would "ensure that no one in Washington is re-elected."

Will Wall Street's complacency come back to bite them?

"The risk of a default is not zero," says Erik Davidson, deputy chief investment officer at Wells Fargo Private Bank. "It is a possibility but not a probability. That's the challenge."

In other words, the consequences of a default, such as a spike in borrowing costs, financial market upheaval, and a hit to the economy and consumer confidence, while low, can't be ruled out completely.

Wall Street, you recall, didn't think the government would let one-time Wall Street titan Lehman Bros. fail in September 2008. But they did. And every investor in America now knows what can happen if a so-called Black Swan event catches the market by surprise.

Indeed, the assumption that Washington politicians are reasonable people and won't allow the country to plunge into default might be a sign of over-confidence in a market-friendly outcome.

She notes that bullishness of individual investors and stock market newsletter writers "has yet to be deterred."

As a result, Adams says the 2011 budget fight, which was resolved at the last minute, but still resulted in the U.S. losing its triple-A credit rating and a major stock selloff, is a good comparison to the market's current woes.

Bruce Bittles, chief investment strategist at R.W. Baird, is also concerned that so many investors are not that concerned about the political gridlock. He points to a dearth of pessimism: Tech stocks are leading the market and initial public offerings, or IPOs, are showing signs of froth.

"I'd be much more comfortable if there were a lot more fear in the market," says Bittles. "A lack of fear leaves little room for error if the market gets a surprise."